This invention relates to a method and device for use in the manufacture of cigarette filters. More particularly, this invention relates to a method and device for very high speed delivery of controlled amounts of a free-flowing material into discrete receiving spaces between individual filter plugs in partially-constructed cigarette filters. The device of this invention has a plurality of conveyance devices, each utilizing vacuum to rapidly and efficiently transfer and accurately place the free-flowing material into the discrete receiving spaces.
Some of the present devices used to transfer a free-flowing material into discrete spaces between filter plugs in cigarette filters are limited in operating speed due to the time required for the free-flowing material to free fall under the influence of gravity. For example, in Williams, U.S. Pat. No. 3,312,152, powder is transferred from a hopper to a pocket vacuum, but later, the powder free falls from that pocket into another pocket solely under the influence of gravity. Still later the powder again free falls from the later pocket into receiving spaces between filter plugs. Once delivered, the delivered powder, together with the filter plugs are transported to the next processing station. During that travel, the powder is subject to jostling, drum vibration and other causes, which may allow some particles to escape from the receiving spaces. The escape of particles from the pocket can be problematic, especially at elevated operational speeds, whereat vibration and jostling becomes more pronounced.
In the production of charcoal filter plugs with a device such as in Williamson, U.S. Pat. No. 3,312,152, the escape of charcoal particles from the receiving spaces can be ruinous to the acceptability of filter plugs produced by the apparatus. Many of the particles which escape become smeared along the periphery of the filter plugs as the plugs are directed through the garniture downstream of the particle transfer apparatus. The smeared particles render an unsightly smear about the edges of the final filter product.
Other devices utilize vacuum but also are limited in the speeds they can operate due to the limited period of contact between a transferring receptacle and a receiving receptacle. For example, in Molins, U.S. Pat. No. 3,312,151, powdered filter material is transferred from a hopper to pockets under vacuum, and then from the pockets to receiving spaces between the filter plugs under vacuum. However, each pocket only registers with the receiving space at one location. The wheel must rotate slowly enough to allow a suitable period of alignment between the transferring pocket and the receiving space. The device in Molins '151 suffers the same disadvantages as the device taught in Williamson '152, being prone to allow particles to escape from the receiving spaces during movement beyond the delivery location.
It would be desirable to replace the present devices with devices utilizing vacuum at all stages of the transfer of the free-flowing material. Vacuum facilitates transfer of free-flowing material at a much more rapid rate than gravity alone. It would likewise be desirable to replace the prior devices with devices utilizing periods of parallel travel between the transferring receptacles and the receiving receptacles. Such parallel travel extends the period of contact between the receptacles, thus expanding the time available for transfer of the free-flowing material while still facilitating a very rapid process. Such use of vacuum and parallel travel would enable a device to deliver a free-flowing material at a much more rapid rate than present devices. Additionally, it would be desirable to have an arrangement where vacuum is applied to receiving spaces such that particles are more completely delivered and positively retained until completion of wrapping operations.